The present technology relates to a solid-state image sensor, a driving method and an electronic apparatus, and specifically, relates to a solid-state image sensor, a driving method and an electronic apparatus capable of securing simultaneity within the whole screen, and reducing the influence of the noise caused by leakage of signals in an image sensor.
CMOS image sensors have been widely used as image sensors in recent years. However, a CMOS image sensor performs readout sequentially pixel by pixel typically, and therefore, is difficult to attain simultaneity within the whole screen.
Namely, the CMOS image sensor performs readout operation of scanning sequentially pixel by pixel or row by row on photocharge generated and accumulated by a photoelectric conversion part. In case of this sequential scanning, that is, in case of a rolling shutter employed as an electronic shutter, it is difficult to match start times and end times of exposure for accumulating the photocharge for all the pixels. Hence, there is a problem that the sequential scanning causes distortion of a captured image in capturing images of a moving subject.
As the electronic shutter, a global shutter is employed in which the start of exposure and the end of exposure are performed identically in their timings for all the pixels in a pixel array, for the sensing usage in which this sort of distortion in image is not allowed, and the subject moving fast undergoes image capturing and/or simultaneity in captured image is expected.
A global shutter device which is a device employing the global shutter as an electronic shutter is provided with charge accumulation sections, for example, composed of semiconductor memories, in pixels. The device employing the global shutter transfers and accumulates charges from photodiodes into the semiconductor memories simultaneously, and after that, reads out them sequentially. Thereby, the simultaneity within the whole screen is secured.
Moreover, there is also proposed one which includes: a surface-embedded region for light receiving which is embedded in part of the upper portion of a semiconductor region and on which light is incident; and a charge accumulation region which is embedded in part of the upper portion of the semiconductor region, is deeper than the surface-embedded region for light receiving in depth of the potential well, and accumulates signal charge generated by the surface-embedded region for light receiving (for example, see Japanese Patent Laid-Open No. 2011-204878).
A CMOS image sensor employing the global shutter completely transfers signal charges generated by surface-embedded regions for light receiving to charge accumulation regions simultaneously for all the pixels, and next transfers them to charge readout regions and reads out them. Herein, in case of light received, for example, from the subject with high luminance during the charge holding, this causes leakage of signals from the surface-embedded region for light receiving to the charge readout region, and causes the noise.
Therefore, the device employing the global shutter expects a measure against the noise caused by the leakage of signals. In the technology of Japanese Patent Laid-Open No. 2011-204878, a light shielding film is selectively provided in the upper portion of the charge accumulation region in order to prevent light from leaking into the charge accumulation region, and thus, signals from being added during the signal charge being held in the charge accumulation region.